the beginning of 1 July 1972 to the end of 31 December 1973

5

the beginning of 1 January 1974 to the end of 31 December 1980

10

the beginning of 1 January 1981 to the end of 30 June 1981

13.5

the beginning of 1 July 1981 to the end of 30 June 1982

14.5

the beginning of 1 July 1982 to the end of 31 December 1983

15.5

the beginning of 1 January 1984 to the end of 31 December 1985

14.5

the beginning of 1 January 1986 to the end of 30 June 1986

18.25

the beginning of 1 July 1986 to the end of 31 October 1987

19.5

the beginning of 1 November 1987 to the end of 29 February 1988

18

the beginning of 1 March 1988 to the end of 28 February 1989

15

the beginning of 1 March 1989 to the end of 31 August 1989

17

the beginning of 1 September 1989 to the end of 31 August 1990

21

the beginning of 1 September 1990 to the end of 28 February 1991

19

the beginning of 1 March 1991 to the end of 31 August 1991

17

the beginning of 1 September 1991 to the end of 28 February 1992

15

the beginning of 29 February 1992 to the end of 31 August 1992

13

the beginning of 1 September 1992 to the end of 31 August 1993

11.25

the beginning of 1 September 1993 to the end of 28 February 1995

10.5

the beginning of 1 March 1995 to the end of 28 February 1997

12

the beginning of 1 March 1997 to the end of 31 August 1997

10.5

the beginning of 1 September 1997 to the end of 31 August 1998

10

the beginning of 1 September 1998 to the end of 29 February 2000

9.5

the beginning of 1 March 2000 to the end of 31 August 2000

10

the beginning of 1 September 2000 to the end of 31 August 2001

11

the beginning of 1 September 2001 to the end of 28 February 2002

10

the beginning of 1 March 2002 to the end of 31 December 2006

9

the beginning of 1 January 2007 to the end of 5 March 2009

10

after 5 March 2009

9